The preferred embodiment concerns a printing system and in particular a method, a control device and a computer program product for monitoring of printed data in a printing system. The preferred embodiment furthermore in particular concerns a method for monitoring of printed data in an electrographic high-capacity printing system.
In electrographic high-capacity printing systems with a print capacity of more than 40 pages per minute, both margin-perforated, ribbon-shaped paper and paper without margin perforation are used as recording media.
In high-capacity printing systems it is necessary that the print data and the printer itself are synchronized per page. For this, a method is known in which at least two print images are printed on each printed sheet, whereby each print image comprises a barcode. This barcode contains consecutive numbers. They can be read by a specific workstation such as, for example, a further printer or printing group or a post-processing station. If deviations of the barcodes result within a sheet, this is assessed as an error.
Instead of the barcode, in principle the page numbers of the printed document can also be used, whereby the printing of a further monitoring mark in the form of the barcode can be omitted.
However, it is not always possible to use the page numbers, in particular when a large print job is comprised of a plurality of individual shorter documents with fewer pages respectively or when the documents comprise no page numbers. The automatic scanning of page numbers is additionally significantly more complicated than that of barcodes.
What is disadvantageous in the previously-known method is that the barcodes used are very large and significantly affect the print image of a printed page.
A method for monitoring of a high-capacity production process for production of printed products is known from U.S. Pat. No. 5,613,669. In this manufacturing process, the sheets to be printed are conveyed in a predetermined direction. An image of the sheet or a section of the printed sheet is recorded by means of a camera. Individual sections of the manufacturing process are synchronized with the method, and the position of the sheets in the manufacturing process is calibrated. Furthermore, this method comprises a control device with which an alarm can be triggered in the event that, for example, the sheets are not correctly merged. This control function evaluates the image acquired by the camera, whereby a predetermined section of the print image or a code (such as, for example, a dash code) is read and evaluated.
A device for automatic identification of the line position emerges from U.S. Pat. No. 3,458,688. In addition to the possibility to identify lines, this device also exhibits a device for identification of different document types. Each document type is identified by means of a binary code that can be printed as a dash code on the document.
U.S. Pat. No. 4,429,217 describes a device and a method for verification of credit cards, insertion of credit cards in corresponding card coverings and stacks of the card coverings in a suitable manner for insertion of the cards into letter envelopes. The cards are typically identified using specific information in the form of alphabetical, numerical or optical characters (for example 1-barcode or I-barcode) or using the information contained on magnetic stripes.
A method for production of folded, bound printed products is described in U.S. Pat. No. 6,363,851. The initial product can be provided with individually-printed markings so that each bound end product exhibits at least one such marking. For example, the page number or a sequence of additional pages can be added by means of this marking. The marking can also represent the end of a specific sequence with which it can then be monitored whether all necessary partial products are present. The marking is preferably printed in a region that is cut off at the end of the production process.
DE 10050 438 C1 discloses a method for synchronization of a plurality of paper-feeding channels of an enveloping system. Every sheet supplied by means of such a channel contains corresponding data or information for designation of the affiliation of the sheet with a specific group, data for designation of the sheet sequence within a group and additional data that specify whether the sheet is a last or consecutive sheet of a group. These data can, for example, be applied on the sheets with the aid of a barcode, a 2 D code, or another suitable coding. The group sequence number can, for example, be comprised of a six-digit numeral series and the sheet sequence number can be comprised of a two-digit numeral series. The designation of a still-running group or of the group examination device can occur in the form of one bit. Given an error, only one group is affected, which group can be sorted out and, for example, supplemented by hand as needed.
Furthermore, in what are known as tandem printing systems it is normally necessary to position with page-precision the print images of both printing devices of the tandem printing system. A tandem printing system is described in U.S. Pat. No. 4,609,279. In U.S. Pat. No. 4,774,524, for activation of such a printing system it is provided to connect the main control devices of both printers via a host computer on a data control level on the one hand and via a second connection on a device control level on the other hand. From U.S. Pat. No. 6,501,929, it is known to synchronize the printed page series in a tandem printing system via an electronic storage. From U.S. Pat. No. 5,488,458, a duplex printing system is known in which a monitoring code is generated and printed for a page to be printed and the printed monitoring code is evaluated. A printing device with two printing groups for simultaneous printing of the front and backsides of a web-shaped recording medium is known from U.S. Pat. No. 6,246,856. The publications cited above are herewith incorporated by reference into the present specification.